Hydrolysis of Al from constrained molecular dynamics

Ikeda, Takashi; Hirata, Masaru ; Kimura, Takaumi 

We investigated the hydrolysis reactions of Al in AlCl aqueous solution using the constrained molecular dynamics based on Car-Parrinello molecular dynamics method. By employing the proton-aluminum coordination number as a reaction coordinate in the constrained molecular dynamics the deprotonation as well as dehydration processes are successfully realized. From our free-energy difference of kcalmol the hydrolysis constant is roughly estimated as 5.8 comparable to the literature value of 5.07. We show that the free-energy difference for hydrolysis of Al in acidic conditions is at least 4kcalmol higher than that in neutral condition, indicating that the hydrolysis reaction is inhibited by the presence of excess protons located around the hydrated ion in agreement with the change of the predominant species by H.